1. Field of the Invention
The present invention relates to water mist fire suppression technology. More specifically, this invention relates to a method and device using microemulsions in the suppression of fire by ultrafine mist droplets.
2. Description of the Prior Art
Water mist based fire suppression systems have been in existence for many years. However, such systems were mostly replaced and the technology forgotten because of the advent of halon gas systems in the 1960's. In recent years, it has been discovered that halon gas is not environmentally safe, and its continued use has been banned due to its alleged potential to deplete ozone in the atmosphere. Thus, there is an urgent need for an alternative fire suppression system, which is effective and environmentally friendly and safe to use.
Because of several favorable properties, water mist has been reconsidered as a potential agent to replace halon gas, in particular in applications for the total flooding of machinery space or other various areas. Water is environmentally friendly with no known toxic properties. Water has a specific heat of 4.18 J/g, and a high latent heat of vaporization of 2260 J/g that assist in cooling a flame. Finally, water is readily available and cost efficient.
Water mist suppresses fire through different mechanisms. Each mechanism exhibits a different degree of influence on the overall suppression efficiency of a water mist. The four important operating mechanisms are heat extraction, oxygen displacement, radiant heat attenuation, and dilution of the vapor/air mixture. Heat extraction and cooling of the flame has the maximum effect on the efficiency of fire suppression and the other mechanisms usually supplement the heat extraction mechanism. The inventors have found that the success of water mist in its application to fire suppression depends on the ability to produce ultrafine droplets of water mist and deliver the mist to various fire scenarios. Extremely small droplets vaporize instantaneously and absorb energy to extract heat from the flame, yielding beneficial suppression properties. Water mist droplets of larger diameters vaporize more slowly and are not as efficient in suppressing fires. Further, smaller droplets increase rates of mist entrainment into the fire plume, thus increasing suppression efficiency in displacing the oxygen fueling the flame. Since heat extraction from the flame and oxygen displacement are most significant in the effectiveness of water mist systems, mechanisms that deliver very fine droplets capable of quick evaporation are desirable.
In known fine water mist fire suppression systems, a directional mist or fog of fine water droplets is generated through a nozzle. Even in the most efficient of these systems, the droplet size often ranges from 80–200 microns, and at best micromist generating technology using high-pressure nozzles appears to produce droplets on the order of 20 micron. Using mechanical high-pressure designs would require expensive and difficult to implement technology to further reduce water droplet scale. Thus, it would be desirable to reduce the droplet size of water mist produced by water mist fire suppression systems by less burdensome methods.